1. Field of the Invention
The present invention relates to an image processing method. More particularly, the present invention relates to an image processing method combining image compression and watermark techniques.
2. Description of Related Art
An image compression technique refers to a technique for compressing an image file with a great data amount into a format with a smaller data amount to facilitate storage and transmission. However, regarding a development of the image compression technique, besides improvement of performance and compression ratio is focused, to prevent image quality from excessive degradation is also a very important issue.
A conventional block truncation coding (BTC) is an image coding technique with advantages of a low complication and a high compression ratio. According to the BTC technique, an image is divided into a plurality of blocks, and the coding is performed while taking the block as a unit. In each of the coded blocks, each pixel is represented by a first or a second value according to a pixel average value of the block and a standard deviation. Therefore, as long as the pixel average value, the standard deviation and a corresponding relation of each pixel and the first or the second value are stored, such block can be represented.
It is easy to deduce that the larger the block used as the coding unit is, the higher compression ratio the generated image has, though the image quality is adversely affected. It is easy to lead to discontinuity of adjacent blocks to generate a blocking effect when the larger block is taken as the coding unit. When the blocking effect is excessively serious, human eyes cannot smoothly recognize features such as edges or outlines of the original image.
Moreover, most of the current image compression techniques focus on reaching a balance among the processing efficiency, the compression ratio and the image quality, though there is no corresponding solution for an information security issue that gradually becomes important recently.